The induction heating apparatus to which the present invention apertains is largely composed of a static power inverter and an induction heating unit which comprises a plurality of heater coils connected between the output terminals of the power inverter. The static power inverter comprises a semiconductor switching circuit consisting of a parallel combination of a silicon controlled rectifier and a diode which are connected in reverse directions to each other. Across the semiconductor switching circuit is connected an oscillating circuit consisting of a commutating inductor and a commutating capacitor so that a high-frequency oscillating current is produced when the silicon controlled rectifier forming part of the switching circuit is triggered at a predetermined frequency. A resonance current is consequently produced in each of the heater coils which usually are connected in parallel between the output terminals of the static power inverter or, more exactly, across the above mentioned commutating capacitor so that a commutating magnetic field is induced by each of the heater coils. The commutating magnetic field produces eddy currents in a cooking pan, pot or kettle placed in the vicinity of each of the heater coils with the result that the material to be cooked is heated directly from the cooking implement in which the material is contained.
According to the prior art, however, when the cooking implement is temporarily removed from a top plate positioned above the heater coils in the process of cooking, the heater coil associated with the removed cooking implement is undesirably and instantly deenergized. Furthermore, the de-energized heater coil affects inversely overall load impedance of the induction heating unit when the plurality of heater coils are driven by single static power inverter.